DESCRIPTION

In this example, we provide a role for the base object class that adds some simple debugging output. Every time an object is created, it spits out a warning saying what type of object it was.

Obviously, a real debugging role would do something more interesting, but this recipe is all about how we apply that role.

In this case, with the combination of Moose::Exporter and Moose::Util::MetaRole, we ensure that when a module does use MooseX::Debugging, it automatically gets the debugging role applied to its base object class.

There are a few pieces of code worth looking at more closely.

Moose::Exporter->setup_import_methods;

This creates an import method in the MooseX::Debugging package. Since we are not actually exporting anything, we do not pass setup_import_methods any parameters. However, we need to have an import method to ensure that our init_meta method is called.

Then in our init_meta method we have this line:

Moose->init_meta(%options);

This is a bit of boilerplate that almost every extension will use. This ensures that the caller has a normal Moose metaclass before we go and add traits to it.

The Moose->init_meta method does ensures that the caller has a sane metaclass, and we don't want to replicate that logic in our extension. If the Moose->init_meta was already called (because the caller did use Moose before using our extension), then calling Moose->init_meta again is effectively a no-op.